The Biomarker Core provides a unique resource to the TTURC investigators. This Core will provide not only biomarker measurements, but also expertise in the interpretation of these data and their application in the design of further research approaches toward reduction of tobacco associated diseases. The work of this Core is highly integrated into all projects of the TTURC. The expertise of this Core in tobacco carcinogenesis, nicotine biochemistry, and carcinogen metabolism adds an important dimension to this TTURC. The work of the Biomarker Core will center around two main broad themes: 1) measurement of nicotine metabolites and biomarkers of carcinogen uptake to assess the relationship of tobacco exposure at various levels to uptake of nicotine and carcinogens and 2) the relationship of nicotine metabolism, as mediated by cytochrome P450 2A6, to susceptibility to cigarette use. The following alkaloids, metabolites, and adducts will be quantified in this work: nicotine metabolites including nicotine-glucuronide, cotinine, cotinine-glucuronide, trans~3?~ hydroxycotinine, and trans-3'-hydroxycotinine-glucuronide; 7- hydroxycoumarin as a measure of cytochrome P450 2A6 activity; 4- (methylnitrosamino)-l-(3-pyridyl)-l-butanol (NNAL) and its glucuronide (NNAL-Gluc) as measures of uptake of the tobacco-specific lung carcinogen 4-(methylnitrosarnino)-I-(3-pyridyl)-l-butanone (NNK); I- hydroxypyrene as a measure of uptake of carcinogenic polycyclic aromatic hydrocarbons; 4-aminobiphenyl-hemoglobin adducts as indicators of the uptake and metabolic activation of the human bladder carcinogen 4- aminobiphenyl; F2-isoprostanes as indicators of oxidative damage associated with cigarette smoking; and metabolites of NNK as influenced by nicotine administration. Collectively, these biomarkers will substantially enhance our understanding of the biochemical and mechanistic aspects of the tobacco exposure reduction strategies being explored in this TTURC.